(1) Field of the Invention
The invention relates to blowers for high efficiency furnaces for drawing combustion gases into the furnace and propelling the products of combustion into the exhaust pipe to be vented to atmosphere. More specifically, the invention relates to the construction of the blower housing.
(2) Description of the Related Art
Blowers to which the present invention is directed are common in the art. The blower is used on high efficiency furnaces (e.g. 90% efficiency) to draw combustion air into the furnace from outside the home. Generally, these blowers are located downstream of a combustion chamber or combustion tubes in the furnace, depending upon the style of furnace. Combustion air is drawn into the combustion chamber or combustion tubes, mixed with fuel, and ignited to generate heat for the furnace. The exhaust gases are then drawn into the suction of the blower and discharged from the blower to an exhaust pipe that vents to outside atmosphere.
FIG. 1A shows a blower 20 of the prior art arranged on a blower mounting surface 21 of a furnace 23. The blower 20 includes a blower motor 47 and a blower housing 24. In FIG. 1A, the blower motor has been removed from its center mount 26 on top of the blower housing 24 to show greater detail of the blower housing 24. The blower housing 24 has a side wall 28 extending between a top piece 30 and a bottom piece 32. Locator surfaces 33A,33B are provided on the top and bottom pieces 30,32 to align the top and bottom pieces 30,32. The locator surfaces 33A,33B also form a seal between the top and bottom pieces 30,32 to contain exhaust gases within the blower housing 24. The top piece 30 is molded with the center mount 26 recessed to receive the blower motor 47. The side wall 28, top piece 30, and bottom piece 32 form a volute 34 for the blower housing 24. When the blower 20 is energized, an impeller (not shown), operably connected to a shaft of the blower motor , rotates in the volute 34 to draw exhaust gases through an inlet hole 35 in the center of the bottom piece 32 and to compress gases in the volute 34. The pressurized exhaust gases are directed into a discharge pipe 36 that extends outward and away from the blower 20 and the furnace 23. Mounting feet 38 for attaching the blower 20 to the blower mounting surface 21 of the furnace 23 are provided on the side wall 28 of the blower housing 24.
FIG. 1B shows the blower 20 arranged on the blower mounting surface 21 in the furnace 23. The blower housing 24 is positioned to allow the impeller (not shown) to draw exhaust gases directly from the combustion chamber or combustion tubes (not shown) into the blower housing 24. The discharge pipe 36 is coupled to an exhaust pipe 39 using a gasket 40 to vent the exhaust gases to atmosphere. The top piece 30 is attached to the blower mounting surface 21 using mechanical fasteners 41 through holes 42 on the mounting feet 38. The mechanical fasteners 41 have a screw head driving end 43 and an opposite driven end 44 spaced from the driving end 43 by a shaft 45. The screw head driving end 43 engages a seating surface 46 on the mounting foot 38 and holds the top piece 30 onto the blower mounting surface 21. The bottom piece 32 is preferably held in position between the top piece 30 and the blower mounting surface 21 by compression from the mechanical fasteners 41.
Typically, the impeller rotates at a high rate of speed to generate sufficient air flow into the combustion chamber and combustion tubes and to draw the exhaust gases out into the exhaust pipe 39. As shown in FIG. 1B, the blower motor 47 is positioned directly atop of the blower housing 24 and the shaft (not shown) of the blower motor 47 is directly coupled to the impeller (not shown) in the blower housing 24. The high speed rotation of the impeller and the motor 47 tends to create noise and other vibrations that are transferred directly into the blower housing 24. As shown in FIG. 1B, the blower 20 is directly mounted onto the blower mounting surface 21 of the furnace 23. Therefore, noise and vibrations are transmitted directly to the blower mounting surface 21 in the furnace 23. This vibration results in unwanted noise being transmitted into the associated structures of the furnace 23 such as ducting where the noise can be transmitted throughout the house. The vibration also contributes to a decreased life span of the blower 20.
In the prior art to combat these problems, the installation of the blower housing onto the furnace mounting surface generally involved installing cushioning mounts 48 and other vibration absorbing gaskets between the blower housing 24 and the blower mounting surface 21. This technique complicates installation and causes a small air gap between the blower housing and the blower mounting surface. Often, the impeller or motor shaft must be dynamically balanced to reduce vibration; however, this process adds manufacturing cost.
What is needed to overcome the disadvantages of the prior art is to form a blower housing which has sound dampening qualities integrally formed in the housing to reduce noise and vibration transmitted from the motor and impeller into the blower mounting surface. Such a blower housing would have the vibration absorbing material integrally formed in the housing so that gaskets and other additional cushioning devices are not needed. Moreover, such a blower housing needs to be sufficiently sturdy to withstand high temperature exhaust gases passing through it.
In order to overcome the disadvantages of the prior art, the blower of the present invention includes a blower housing having a resilient bottom piece and a rigid top piece covering over the bottom piece to enclose an interior of the blower housing. The bottom piece of the blower housing is preferably cylindrically shaped and directly abuts the exterior mounting surface of the furnace with cushioned mounting flanges provided. The top piece of the blower housing is secured to the bottom piece and also provides the support for mounting the blower motor as explained below.
The bottom piece of the blower housing may be made from a vibration dampening material. Preferably, materials such as sanoprene and viram are suitable for dampening and attenuating vibrations and withstanding the heat from the products of combustion which flow through the blower housing. The top piece of the blower housing may be made from a material such as polypropylene to provide a rigid mount for the blower motor and with what may preferably be integrally formed depending mounting legs, the rigid mount for the motor extends to the furnace housing as explained below.
The top piece of the blower housing includes an annular central lower support portion for supporting the blower motor and an annular upper portion extending above and around the lower portion. The upper portion of the top piece of the blower housing has an outer peripheral edge and preferably a plurality of lugs extending outwardly beyond the outer peripheral edge. The bottom piece of the blower housing has preferably a plurality of flanges that align with the lugs when the blower housing is assembled. The flange interlocks with the lug to detachably engage the top piece to the bottom piece. The top piece, side wall and bottom piece form a volute for the blower housing.
The lugs on the top piece have a lug hole to receive a mechanical fastener such as a screw or bolt and provide the surface against which the mechanical fastener is snugged as it is tightened to mount the blower. The flanges on the bottom piece preferably have flange holes that receive the mechanical fasteners therethrough as the mechanical fasteners join the top piece to the blower mounting surface of the furnace. The mechanical fasteners preferably attach the blower housing to a blower mounting surface of the furnace such that the blower housing is positioned between a blower motor and an exterior mounting surface of the furnace.
To provide further structural integrity to the top and bottom pieces when the housing is assembled, the lugs on the top piece are preferably provided with a depending leg. The depending leg extends downwardly and away from the outer peripheral edge of the top piece and is received and cushioned in an associated flange hole. The mechanical fasteners thus are inserted through the lugs, beneath the depending legs, through the flange holes, and into the furnace to mount the blower housing. Thus the rigid mount for the motor is achieved while being cushioned by the cushioning flanges of the bottom piece.
The blower housing of the present invention may be installed on a furnace without the use of sound absorbing or other vibration dampening devices separate from the actual blower housing materials themselves and yet provide a relatively vibration and noise free installation. The blower housing of the present invention eliminates the need for balancing of the motor shaft and/or impeller to reduce undesirable vibrations.